tbh, i never knew toxic reader is even a common thing.
They are rather rare. The problem is that people who are toxic/agitated often have more motivation to leave a comment on your writing or review compared to the silent readers that just enjoy your story.
In my case, there are a handful of positive readers who comment on every chapter (even if it's only "Thanks for the chapter" as support), I have some readers who only comment on "big chapters" or when something unexpected happened, and the overwhelming majority of readers is silent.
When you have a toxic/agitated reader, they often leave a bad comment on each chapter. So one new toxic/agitated reader can mean 30 new comments and 28 of them are hurtful. That can kill all the motivation. Back then, I had someone who even wrote PMs and attacked me personally and it pushed me away from writing for more than a year.
Though there is also a difference between toxic readers, agitated readers (some who wrote negative reviews even apologized and changed them when I just wrote them a nice message thanking them for their feedback or pointing some stuff out without going "You are wrong"), and honest feedback based on their personal scale.
But in the end, negative stuff just hurts that much more and stays a lot longer in your mind. It's the same reason we have a hundred threads about "early 1 star ratings" but none about "early 5 star ratings". And that can also "inflate" the numbers of toxic readers, because a lot of authors don't talk about all the nice support they are getting.
I literary had people come to me and say "To me, this is the best story on SH and I come every day to check for an update" and yet I put a lot more thought on a "This is boring shit"-comment that openly showed that he didn't understand the tags or the core of the story.
It's a learning process to accept the problems with your writing, to accept that there'll always be people who are toxic no matter what you do, and to see the fun and motivating things in writing. But when you are a new writer with only a handful comment and go through people writing you daily messages to kill yourself, this learning experience can come at the expence of a dropped novel and some time off...